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| 2. |
- Enger, Shirin A., et al.
(författare)
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Gadolinium neutron capture brachytherapy (GdNCB), a new treatment method for intravascular brachytherapy
- 2006
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Ingår i: Medical physics (Lancaster). - : Wiley. - 0094-2405. ; 33:1, s. 46-51
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Tidskriftsartikel (refereegranskat)abstract
- Restenosis is a major problem after balloon angioplasty and stent implantation. The aim of this study is to introduce gadolinium neutron capture brachytherapy (GdNCB) as a suitable modality for treatment of stenosis. The utility of GdNCB in intravascular brachytherapy (IVBT) of stent stenosis is investigated by using the GEANT4 and MCNP4B Monte Carlo radiation transport codes. To study capture rate, Kerma, absorbed dose and absorbed dose rate around a Gd-containing stent activated with neutrons, a 30 mm long, 5 mm diameter gadolinium foil is chosen. The input data is a neutron spectrum used for clinical neutron capture therapy in Studsvik, Sweden. Thermal neutron capture in gadolinium yields a spectrum of high-energy gamma photons, which due to the build-up effect gives an almost flat dose delivery pattern to the first 4 mm around the stent. The absorbed dose rate is 1.33 Gy/min, 0.25 mm from the stent surface while the dose to normal tissue is in order of 0.22 Gy/min, i.e., a factor of 6 lower. To spare normal tissue further fractionation of the dose is also possible. The capture rate is relatively high at both ends of the foil. The dose distribution from gamma and charge particle radiation at the edges and inside the stent contributes to a nonuniform dose distribution. This will lead to higher doses to the surrounding tissue and may prevent stent edge and in-stent restenosis. The position of the stent can be verified and corrected by the treatment plan prior to activation. Activation of the stent by an external neutron field can be performed days after catherization when the target cells start to proliferate and can be expected to be more radiation sensitive. Another advantage of the nonradioactive gadolinium stent is the possibility to avoid radiation hazard to personnel.
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| 3. |
- Enger, Shirin A., et al.
(författare)
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Monte Carlo calculations of thermal neutron capture in gadolinium : a comparison of GEANT4 and MCNP with measurements
- 2006
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Ingår i: Medical physics (Lancaster). - : Wiley. - 0094-2405. ; 33:2, s. 337-341
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Tidskriftsartikel (refereegranskat)abstract
- GEANT4 is a Monte Carlo code originally implemented for high-energy physics applications and is well known for particle transport at high energies. The capacity of GEANT4 to simulate neutron transport in the thermal energy region is not equally well known. The aim of this article is to compare MCNP, a code commonly used in low energy neutron transport calculations and GEANT4 with experimental results and select the suitable code for gadolinium neutron capture applications. To account for the thermal neutron scattering from chemically bound atoms [S(alpha,beta)] in biological materials a comparison of thermal neutron fluence in tissue-like poly(methylmethacrylate) phantom is made with MCNP4B, GEANT4 6.0 patch1, and measurements from the neutron capture therapy (NCT) facility at the Studsvik, Sweden. The fluence measurements agreed with MCNP calculated results considering S(alpha,beta). The location of the thermal neutron peak calculated with MCNP without S(alpha,beta) and GEANT4 is shifted by about 0.5 cm towards a shallower depth and is 25%-30% lower in amplitude. Dose distribution from the gadolinium neutron capture reaction is then simulated by MCNP and compared with measured data. The simulations made by MCNP agree well with experimental results. As long as thermal neutron scattering from chemically bound atoms are not included in GEANT4 it is not suitable for NCT applications.
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| 4. |
- Knöös, Tommy, et al.
(författare)
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Modelling of an Orthovoltage X-ray Therapy Unit with the EGSnrc Monte Carlo Package
- 2007
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6596 .- 1742-6588. ; 74, s. 86-95
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Konferensbidrag (refereegranskat)abstract
- Simulations with the EGSnrc code package of an orthovoltage x-ray machine have been performed. The BEAMnrc code was used to transport electrons, produce x-ray photons in the target and transport of these through the treatment machine down to the exit level of the applicator. Further transport in water or CT based phantoms was facilitated by the DOSXYZnrc code. Phase space files were scored with BEAMnrc and analysed regarding the energy spectra at the end of the applicator. Tuning of simulation parameters was based on the half-value layer quantity for the beams in either Al or Cu. Calculated depth dose and profile curves have been compared against measurements and show good agreement except at shallow depths. The MC model tested in this study can be used for various dosimetric studies as well as generating a library of typical treatment cases that can serve as both educational material and guidance in the clinical practice
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| 5. |
- Munck af Rosenschöld, Per, et al.
(författare)
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Prompt gamma tomography during BNCT – a feasibility study
- 2006
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 1
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Tidskriftsartikel (refereegranskat)abstract
- The success of clinical boron neutron capture therapy (BNCT) lies in the ability to manage the radiobiological effect on the tumour and healthy tissue, and thus, accurate dosimetry measurements is pertinent for each individual patient. In the present work we investigate the possibility of performing online prompt gamma tomography (PGT) during BNCT. A prototype detector system was constructed, which is in principle a pin-hole collimator with a HPGe crystal to be mounted on a C-bow device, with shielding of lithium-plastic and lead. The detector system was used to measure on a phantom placed in an epithermal neutron beam and on a 137Cs-source. The possibility of tomographic reconstruction using the detector system was tested on a phantom filled with a 131I-solution with a smaller sphere inserted containing a higher specific activity (ratio 10:1). The detector system was possible to operate up to about 6 × 108 cm-2 s-1 thermal neutron fluence at the peak in the phantom, at which time it was saturated. A 478 keV boron-peak was visible in the measured spectra but the signal-to-noise-ratio was rather low. No post-irradiation damage or neutron activation was detectable. A tomographic reconstruction of the phantom filled with 131I-solutions was performed using an algorithm developed in house and based on the MLEM method. The image quality is fairly good and the results provide a clear indication that the detector system can be used to obtain data that enables tomographic reconstruction. A spatial resolution of the detector system of about 2 cm was obtained from both the measurement on the 137Cs-source and the 131I-phantom. In conclusion, the presented feasibility study on a prototype PGT system is encouraging further studies specifically directed at improving the signal-to-noise-ratio in measurements in epithermal neutron beams.
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| 6. |
- Persson, Bertil R, et al.
(författare)
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Survival of rats with N29 brain tumours after irradiation with 5 or 15 Gy and immunization with IFN-gamma secreting tumour cells
- 2008
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Ingår i: BioMedical Engineering and Informatics : New Development and the Future - Proceedings of the 1st International Conference on BioMedical Engineering and Informatics, BMEI 2008 - New Development and the Future - Proceedings of the 1st International Conference on BioMedical Engineering and Informatics, BMEI 2008. - 9780769531182 ; 2, s. 243-247
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Konferensbidrag (refereegranskat)abstract
- Intra cerebral tumours were inoculated into the brain of Fischer-344 syngeneic rats. After one week they were treated with either 5 or 15 Gy of Co-60-gamma radiation. The first immunization was given 1 hour before the radiation treatment and then two more times with 14-day intervals. Immunization was performed with 3 x 10(6) radiation sterilized IFN-gamma secreting tumour cells (N29) injected intraperitoneally. Neither radiation therapy with 5 or 15 Gy nor immunization with N29 cells alone had any significant effect on the length of survival of N29 tumour bearing rats. But radiation therapy with 5 Gy combined with immunization with IFN-gamma secreting syngeneic N29 cells resulted in 63 % complete remissions and significantly (p < 0.05) increased survival for the tumour bearing rats. Corresponding combination with 15 Gy RT resulted in 50% complete remissions. There is a possibility of a synergistic effect by optimal combination of radiation therapy and immunization.
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